Conventionally, for example, when transmitting a video signal to a liquid crystal monitor or a CRT, analog transmission using an analog RGB interface has been in the mainstream. However, the number of displayable pixels has previously been determined in the liquid crystal monitor, and digital transmission has received attention with proliferation of the liquid crystal monitor. Further, an increase in refresh rate is needed for a reduction in flicker, and high-speed data transmission is needed for image display on a wider screen. Since, in the conventional analog transmission, transmission distortion is considerable and ghosts are likely to occur, importance of digital transmission is increasing with improvement in image quality.
With the needs for digital transmission, in recent years, DVI (Digital Visual Interface) has received attention. The DVI is an interface for digital display connection which is defined by DDWG (Digital Display Working Group), and transfers data using plural data channels on the basis of TMDS (Transition Minimized Differential Signaling) technique. When adopting a digital transmission method using the DVI, high-quality video data with less transmission distortion can be provided by digital transmission at low cost.
As described above, by the adoption of the DVI, a higher-quality image can be obtained as compared with analog transmission. Further, in the DVI, there exists a blanking period when other data can be transmitted, besides a period for transmitting RGB (Red, Green, Blue) pixel data. It is possible to transmit, for example, an audio signal using this blanking period.
When transmitting a digital video signal, a transmission error such as bit corruption sometimes occurs. However, even when such transmission error occurs in transmitting a video signal, it is not very conspicuous on screen and, therefore, no serious problem occurs. However, when a transmission error occurs during transmission of an audio signal, noise or unusual sound might occur and, therefore, the error rate must be considered more strictly than in the case of transmitting a video signal. That is, when transmitting error-conspicuous data other than a video signal by using the blanking period of the DVI or the like, processing for error detection and error correction is required independently. However, in the standard of the interface for digital display connection which is defined by the DDWG (Digital Display Working Group), a construction for error detection and error correction for an audio signal has not been proposed.
The present invention is made to solve the above-described technical problems and has for its object to provide an error-correction coding method, an error-correction coding apparatus, an error-correction decoding method, and an error-correction decoding apparatus, which can perform error detection and error correction for an audio signal when transmitting multiplexed video signal and audio signal by a DVI.